A virtual machine (VM) is a computer system that simulates functions of a complete hardware system by using software, and operates in an isolated environment. By implementing VM technologies, a physical computer may emulate one or more virtual computers. Like a physical computer, a VM may, for example, install operating systems as well as applications and accesses the Internet resources.
In general, data of a VM is stored in a virtual disk of the VM. The virtual disk is stored in a physical disk of a local physical computer in the form of mirror documents, logic virtual volumes, logic disks or logic disk partitions. The VM may access the data by accessing the physical disk of the local computer. This may present problems, for example, when the local computer is shut down or damaged.